Moving object detection plays an important role in automatic surveillance systems. Surveillance systems detect abnormal security events by analyzing the trajectory and behavior of moving objects in an image, and notify the related security staff. The development of the security robots moves towards the intelligent security robots with abnormal event detection capability to support dynamic deployment and repetitive, continuous surveillance. The moving object detection aims to replace the passive recording widely used in conventional surveillance systems.
For example, US. Pat. No. 6,867,799 disclosed a method and apparatus for object surveillance with a movable camera, including the construction of a surveillance mechanism of maintaining a moving object of interest within the filed of view of a movable camera in an object surveillance system. According to the selected object of interest, the camera movement commands are created so that the object of interest remains in the field of the view of the camera. U.S. Pat. No. 7,123,745 disclosed a method and apparatus for detecting moving objects in video conferencing and other applications. From the continuous video images of a fixed camera, the difference image technique is used to detect moving person and the position and the size of the head of the person are identified.
U.S. Pat. No. 5,991,428 disclosed a moving object detection apparatus and method, including a foreground moving object detection technique applicable to a platform with a movable camera. By image segmentation, template matching and evaluation and voting, the disclosed patent estimates the moving vector of the corresponding areas of the neighboring images. Based on the dominant moving vector of the image, the align vector between the neighboring images is determined. Based on the align vector, one of the two neighboring images is shifted for alignment and difference comparison to identify the moving object area. U.S. Pat. No. 5,473,364 disclosed a video technique for indicating moving objects from a movable platform. Assuming that the images captured by the front and rear cameras at two consecutive times have only a slight difference, the disclosed patent aligns the images from the front camera and subtracts from the image from the rear camera, and then uses Gaussian pyramid construction to compute the area energy to detect the moving objects and obtains more stable moving object profiles.
However, image-based moving object detection technique deployed on a fixed camera usually cannot provide dynamic security support. In a restricted surveillance area, the surveillance is often ineffective. On the other hand, for movable camera surveillance, the movement of the camera will cause the entire image change and the compensation to the error caused by the camera movement makes it difficult to use a single image-based technique to effectively detect moving objects.
FIGS. 1 and 2 show the moving object detection methods, which integrate background subtraction and consecutive image difference, proposed by Desa and Spagnolo in 2004 and 2006 respectively. The background subtraction is to consider the background of an area in foreground detection, and the consecutive image difference is to find the difference in a plurality of consecutive images to detect moving parts. However, in the techniques depicted in FIGS. 1 and 2, the background subtraction and consecutive image difference are solely integrated computationally. Therefore, only the outer profile of moving objects can be detected, while the inner area of the entire moving objects cannot be detected.